High-frequency coil



- Nov. 8, 1938.

W. J. POLYDOROFF. El" AL HIGH FREQUENCY COIL Filed Feb. 10, 1956 INVENTOR-5 HzAwM/EJPuYa eoFF Patented Nov. 8, 1938 a UNITED STATES PATENT OFFICE 2,135,841 mcnrasounncr con.

Wladlmir J. Polydoroil, Wilmette, and Dwight V. Sinninger, Chicago, Ill., assignors to Johnson Laboratories, Inc., Chicago, 111., a corporation of Illinois.

Application February 10, 1936, Serial No. 63,100 3 Claims. (Cl. 250-40) The invention relates to high-frequency cou- I supports from its upper closed end a coil pling devices suitable for in radio receivers, and trimmer capacitor assembly II, the upper and more particularly to such devices for use in end of each can i being provided with holes to receivers intended {or the reception of several receive coil adjusting screws l2 and to permit 5 bands of frequencies. l r access to the trimmer capacitors. 5

When the circuits are tuned by variable capac- If the device of Fig. 1 is to be employed in a itors, the desired spectrum of frequencies usually tuned radio-frequency receiver, 4 the three" asis divided into several bands, depending on the semblies H are identical. For use in superheterorange of variability of the variable capacitors. dyne receivers, however, one of the assemblies It is practical to employ variable tuning capaci- Ii may be diflerent from the others and emtors having a capacitance range between 10 and ployed in conjunction with the oscillator sys- 450 micromicrofarads, which, in parallel with the tem of the receiver. In Fig. 1, the middle unit is initial capacitance of the circuit and vacuum intended for this purpose. The leads from the tubes, will cover a range of frequencies having a assemblies ii are brought out to the terminal maximum ratio of about 3. lugs of switch sections 4, so that the whole as- An object o! the invention is to provide a highly sembly is compact and self-supporting, and may eillcient coil system-for use in multiple-band rebe assembled and tested before being installed in ceivers of either the tuned radio-frequency or the radio receiver of which it is to form a comsuperheterodyne type. Another object of the inponent part. Furthermore, each assembly ii is '20 vention is to provide means for equalizing the thoroughly shielded both from the other ,assemwand performance of several coil systems which are blies and from other component parts of the simultaneously tuned. A further object of the receiver. r invention is to provide a compact and fully Referring to Fig. 2, spade bolts ii are attached shielded coil system readily adapted for mounting to coil form I and pass through insulating base in a radio receiver. i5, which carries two adjustable trimmer capac- 25 The invention will be better understood by ref- -itors it. The short-wave coil i1 having a prierence to the accompanying drawing, in which: mary winding is wound on the coil form ll. Fig. 1 is an elevation of a group consisting of Coil lI preferably consists of a single layer of a three coil systems according to the invention, solid insulated conductor. Centrally located in insulating base I! is a threaded bushing i8 30 Fig} 2 is a section taken on the line 2-4 of adaptedto receive adjusting screw ii, to the lower Fl!- 1- end of which is attached a small pellet of mag- In. the embodiment of the invention shown in netic material is. Rotation of screw l2 produces the drawing and described herein, each coil sysdisplacementof the pellet i! with respect to the tern includes three coils, arranged to cover three coil i1, thus permitting the inductance of the 35 frequency bands, as follows: the long wave coil to be varied over a limited range. band from 140 to 410 kilocycles; the standard At its lower end, coil form it has attached to broadcast band from 540 to 1700 kilocycles; and it a disc or plate of insulating material 20, from theshort-wave" band from 5.5to 18 megacycles. which is suspended coil torm 2| by means of so It will be understood that it is within the scope of spacer bolts 22. Plate 20 may also support aux- 40 the invention to arrange the coils to have a iliary apparatus, such as for example fixed cadiflerent frequency coverage, either with respect pacltor 23 and terminal lugs 24. On coil form ii to the number of frequency bands or with respect is wound the sectionalized broadcast secondary to the frequencies included in each band. .coll 25, which is provided with a finely com- Referring to Fig. 1, shield cans I are mounted minuted ferromagnetic core II, and a primary 45 by means of spade bolts 2 on metal strips {which winding 3 l. Coil 25 is preferably wound with Litz also support switch sections 4 at either end. The wire, which consists of a number of individually switch sections 4 are operated simultaneously by insulated strands. One trimmer capacitor it is shaft 5, which carries knob i. The shield can connected in shunt with coil 25 and one in shunt and switch section assembly is secured to the with coil iv'l. 50 chassis 1 of the radio receiver or other apparatus The spade bolts 2 also hold in place insulating in which it is a component part by means of strip 21, which supports long-wave coil 2 and j threaded bushing l and out 9. Further support its trimmer capacitor 28, which is readily adjustmay be provided by securing'arm II to another able from below. Ample space is. provided at portion of chassis I, not shown Each shield can either side of strip 21 for the leads from the trim- 5s mer capacitors I! and the terminals II to the switch sections 4, so that a compact and efiicient assembly of the three coils and their trimmer capacitors is obtained.

In operation, the position of pellet it is adiusted until coil I! has the proper inductance at the low-frequency end of the short-wave band of frequencies. Then the trimmer capacitor it which shunts coil I1 is adjusted at the high-frequency end of the short-wave band. In this way, coil l1 need be only approximately of the correct initial inductance with a resultant substantial saving in the cost of manufacture. The trimmer capacitors in shunt with the broadcast and longwave coils, respectively, are adJusted at the highfrequency ends of the frequency bands which each of these coils is intended to cover, in the usual manner.

One of the features of the invention is the provision of simple and inexpensive means for compensating for slight variations in the short-wave coils and in the length and position of their connecting leads, thus substantially improving the performance when several coil systems are simultaneously tuned by means of a multiple-gang variable capacitor. Thus the necessity for great care and uniformity in the manufacture of the shortwave coils is no longer essential for satisfactory performance, and the results are not inherently dependent upon the chance positioning and lengths of the connecting leads.

Having thus described our invention, what we claim is:

1. A multiple-band coil system for use in highfrequency resonant circuits, including an openended shield can containing and supporting a first coil having an adjustable magnetic body, a

-second coil having a fixed ferromagnetic core mounted at right angles to said first coil and trimmer capacitors associated with said first and second coils, and a third coil and associated trimmer capacitor mounted in the open end of said shield can.

.2. A multiple-band coil system for use in highfrequency resonant circuits, including in combination, a multiple-section band-selecting gang switch, a plurality of shield cans, means for mounting said shield cans as a unit with said gang switch, each of said shield cans containing and supporting a first coil having an adjustable magnetic body, a second coil having a fixed ferromagnetic core mounted at right angles to said firstcoil and trimmer capacitors associated with said first and second coils, and a third coil and associated trimmer capacitor mounted in the open end of each of said shield cans.

3. A multiple-band coil system for use in highfrequency resonant circuits, including in combination, a multiple-section band-selecting gang switch, a plurality of open-ended shield cans, means for mounting said shield cans as a unit with said gang switch, each of said shield cans containing and supporting a first coil having an adjustable magnetic body to vary the indutance thereof, a second coil having a fixed ferromagnetic core and mounted with its axis at right angles to the axis of said first coil and intersecting the axis of said first coil externally of said first coil, trimmer capacitors associated with said first and second coils, and connections from said gang switch to said coils, the sections of said gang switch being mounted upon said shield cans and adjacent the open ends thereof in such manner as to minimize the length of said connections.

WLADIMIR J. 'POLYDOROP'I". DWIGHT V. smnmam 

